Transmission apparatus and method, in particular for use in a low throughput network

ABSTRACT

A transmission apparatus, in particular for use in a Low Throughput Network, comprises an FEC encoder configured to encode payload data into FEC code words each having a predetermined code word length, and a frame forming section configured to form a frame having a predetermined frame length. A frame comprises a first frame portion having a first predetermined length of an integer multiple of the predetermined code word length and a second frame portion having a second predetermined length shorter than the predetermined code word length. The frame forming section is configured to include an FEC code word and a predetermined number of repetitions of said FEC code word into the first frame portion of a frame and to include a selected number of bits of said FEC code word into the second frame portion of said frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is continuation of U.S. application Ser. No.16/603,237, filed Oct. 7, 2019, which is based on PCT filingPCT/EP2018/059424, filed Apr. 12, 2018, and claims priority to EP17166343.8, filed Apr. 12, 2017, the entire contents of each areincorporated herein by reference.

BACKGROUND Field of the Disclosure

The present disclosure relates to a transmission apparatus and acorresponding transmission method, in particular for use in a LowThroughput Network (LTN) for Internet of Things (IoT) applications orfor use in a similar network. The present disclosure relates further toa receiving apparatus and a corresponding receiving method, inparticular for use in an LTN.

Description of Related Art

ETSI's standardization group dedicated to LTN technology recentlyreleased the first specifications (including GS LTN 001 containing theuse cases, GS LTN 002 describing the functional architecture and GS LTN003 defining the protocols and interfaces) of an IoT network dedicatedto low throughput communications. LTN technology is a wide areaunidirectional or bidirectional wireless network with keydifferentiators compared to existing networks. It enables long-rangedata transmission (distances around 40 km in open field) and/orcommunication with buried underground equipment and operates withminimal power consumption allowing several years of operation even withstandard batteries. This technology also implements advanced signalprocessing that provides effective protection against interference.

As a consequence, LTN is particularly well suited for low throughputmachine to machine communication where data volume is limited and lowlatency is not a strong requirement. Applications include remotemeasurement, smart metering for water, gas or electricity distribution,positioning or smart cities applications such as air pollutionmonitoring or public lighting. LTN could also cooperate with cellularnetworks to address use cases where redundancy, complementary oralternative connectivity is needed.

LTN IoT networks have a similar topology to existing networks used forhigh data rates and dynamically adapt power and frequency in the sameway, but will also manage new requirements concerning power consumptionand the number of base stations required to cover an entire country. Lowpower, very low throughput, long battery life, simple, effective androbust radio communication principles are the key features of the firstETSI LTN specifications.

There is a need for defining an efficient transmission stream and itsconstruction for use in an LTN.

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventor(s), to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentdisclosure.

SUMMARY

It is an object to provide a transmission apparatus and a correspondingtransmission method, in particular for use in an LTN, for constructingan efficient transmission stream. It is a further object to provide acorresponding receiving apparatus and a corresponding receiving method,in particular for use in an LTN, as well as a corresponding computerprogram for implementing said methods and a non-transitorycomputer-readable recording medium for implementing said methods.

According to an aspect there is provided a transmission apparatus, inparticular for use in an LTN, comprising:

-   -   an FEC encoder configured to encode payload data into FEC code        words each having a predetermined code word length, and    -   a frame forming section configured to form a frame having a        predetermined frame length, wherein a frame comprises a first        frame portion having a first predetermined length of an integer        multiple of the predetermined code word length and a second        frame portion having a second predetermined length shorter than        the predetermined code word length, wherein said frame forming        section is configured to include an FEC code word and a        predetermined number of repetitions of said FEC code word into        the first frame portion of a frame and to include a selected        number of bits of said FEC code word into the second frame        portion of said frame.

According to a further aspect there is provided a receiving apparatus,in particular for use in an LTN, comprising

-   -   a frame extraction section configured to extract one or more        frames from a received transmission stream, a frame including        payload data encoded into FEC code words each having a        predetermined code word length and a frame having a        predetermined frame length, wherein a frame comprises a first        frame portion having a first predetermined length of an integer        multiple of the predetermined code word length and a second        frame portion having a second predetermined length shorter than        the predetermined code word length, wherein said frame        extraction section is configured to extract an FEC code word and        a predetermined number of repetitions of said FEC code word from        the first frame portion of a frame and to extract a selected        number of bits of said FEC code word from the second frame        portion of said frame, and    -   an FEC decoder configured to decode payload data from the FEC        code words, the repetitions of said FEC code word and the        selected number of bits of said FEC code word extracted from        said frame.

According to still further aspects a computer program comprising programmeans for causing a computer to carry out the steps of the methoddisclosed herein, when said computer program is carried out on acomputer, as well as a non-transitory computer-readable recording mediumthat stores therein a computer program product, which, when executed bya processor, causes the method disclosed herein to be performed areprovided.

Embodiments are defined in the dependent claims. It shall be understoodthat the disclosed methods, the disclosed computer program and thedisclosed computer-readable recording medium have similar and/oridentical further embodiments as the claimed apparatus and as defined inthe dependent claims and/or disclosed herein.

One of the aspects of the disclosure is to propose an efficient framebuilding for use in an LTN, by which particularly an improved decodingcan be achieved and the error rate can be improved. A frame may be madeup of several repetitions of the FEC code word, but also includes afraction of a code word. Optimum choices for such partial repetitionsare proposed.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a diagram illustrating an example of transmitting the samepacket a plurality of times in a new communication method.

FIG. 2 is a diagram showing an example of reception of a packet on thereceiving side in a new communication method.

FIG. 3 is a diagram showing an example of frequency hopping.

FIG. 4 is a diagram showing an example of a radio system in whichinterference can occur.

FIG. 5 is a diagram showing an example of interference occurring whenfrequency hopping is performed in a wireless system.

FIG. 6 is a diagram showing a configuration example of a positionnotification system which is an embodiment of a wireless system to whichthe present technology is applied.

FIG. 7 is a block diagram showing a configuration example of atransmission device 101.

FIG. 8 is a block diagram showing a configuration example of a receptiondevice 112.

FIG. 9 is a diagram showing an example of a first format of data handledby a transmitting apparatus 101.

FIG. 10 is a diagram showing an example of a second format of datahandled by a transmission device 101.

FIG. 11 is a block diagram showing a configuration example of akeystream generating unit 211.

FIG. 12 shows a first embodiment of a frame.

FIG. 13 shows a second embodiment of a frame.

FIGS. 14A to 14H show several embodiments of repeating different partsof a code word in a second frame portion of a frame as shown in FIG. 12.

FIGS. 15A to 15I show several embodiments of repeating different partsof a code word in a second frame portion of a frame as shown in FIG. 13.

DETAILED DESCRIPTION OF THE EMBODIMENTS

First, an outline of a new communication method for LPWA (Low Power WideArea) communication to which the present technology is applied will bedescribed. LPWA communication is a wireless communication capable oftransmitting information in a wide range of several tens to 100 km withlow power consumption for use e.g. in IoT devices for transmitting asmall amount of information such as sensor information. In the newcommunication method, for example, a wireless signal is transmitted inthe unlicensed 868 or 920 MHz band. In this case, it can be said thatthe new communication system is a kind of wireless communication in the920 MHz band.

In Japan, the 920 MHz band is a frequency band released from July 2011by the Ministry of Internal Affairs and Communications, and anyone canuse it without a license. However, with regard to wireless communicationin the 920 MHz band, the maximum continuous transmission time is limitedto 4 seconds by the provision (Association of Radio Industries andBusinesses, ARIB, (STD T-108)). Furthermore, if the continuoustransmission time is shortened to, for example, 0.4 seconds or less, theinfluence of interference given to other systems using the samefrequency band can be reduced. Therefore, in the ARIB regulation of the920 MHz band, it is stipulated that more channels can be allocated bysetting the continuous transmission time to 0.4 seconds or less. As aresult, if it is set to 0.4 seconds or less, transmission and receptioncan be performed with less interference. If the continuous transmissiontime is further shortened to 0.2 seconds or less, the pause time can beshortened and retransmission can be performed. In the new communicationmethod, for example, the same packet is transmitted a plurality of timesin order to improve the S/N ratio (Signal to Noise ratio, SNR) of thereception signal on the reception side.

FIG. 1 is a diagram showing an example of transmitting the same packet aplurality of times in the new communication method.

In FIG. 1 , a 1 minute superframe (Superframe) is set, during which thesame packet has been transmitted ten times. In the new communicationmethod, the transmitting side carries out carrier sensing at the time oftransmission. In the new communication method, for carrier sense, asuper frame of one minute is set for ten packet transmissions, forexample, as shown in FIG. 1 .

FIG. 2 is a diagram showing an example of reception of a packet on thereceiving side in the new communication method.

The receiving side receives up to ten packets from the transmitting sideand synthesizes these (ten) packets as shown in FIG. 2 to generate acombined signal (lf signal quality is not sufficiently good, thereceiver might only find less than ten packets from the transmittingsignal). Then, the receiving side extracts data from the synthesizedsignal and outputs it by carrying out decoding (error correction) etc.of the synthesized signal. In this way, by synthesizing the packets togenerate a combined signal, the S/N ratio can be improved. For example,if 10 packets can be added (synthesized), the S/N ratio can be improvedby about 10 dB.

Therefore, in the new communication method, even if the S/N ratio of onepacket is low, it is possible for the receiving side to acquire data,enabling longer distance information transmission. In addition, in thenew communication method, by setting the packet transmission time to 0.2seconds or less, or 0.4 seconds or less as described above, it ispossible to use more frequency channels without being restricted by ARIBregulation. With the new communication method, for example, frequencyhopping using a plurality of carrier frequencies can be performed.

FIG. 3 is a diagram showing an example of frequency hopping. In thefrequency hopping of FIG. 3 , five channels CH 1 to CH 5 are prepared,and each packet is selected by transmitting one of these five channels.As a channel selection method, a method of increasing the transmissionchannel number according to the transmission order, a method ofdetermining the transmission channel number according to a predeterminedmathematical expression, a method of randomly selecting the transmissionchannel number, or the like can be done. According to such frequencyhopping, the occurrence of interference can be reduced.

FIG. 4 is a diagram showing an example of a radio system in whichinterference can occur. The radio system of FIG. 4 has a plurality oftransmitters (transmitter A through transmitter C) and a receiver. Inthe wireless system of FIG. 4 , a plurality of transmitters sometimestransmit radio signals at the same carrier frequency at the same time.When a plurality of transmitters transmits radio signals at the samecarrier frequency at the same time, interference occurs in the receiver,and it becomes difficult to correctly receive the radio signals fromeach of the plurality of transmitters.

Therefore, the frequency hopping of FIG. 3 is applied to the radiosystem of FIG. 4 . In this case, the possibility that the carrierfrequencies become the same can be reduced, and the occurrence ofinterference can be suppressed correspondingly. However, since thewireless system of FIG. 4 is a one-way communication, even if frequencyhopping is performed, there is a possibility that carrier frequencies ofa plurality of transmitters may be the same so that interference is notcompletely generated It is difficult to do.

FIG. 5 is a diagram showing an example of interference occurring whenfrequency hopping is performed in the wireless system. In FIG. 5 ,frequency hopping is performed in the transmitters A and B. However, ata same time, when a certain packet transmitted from the transmitter Aand a certain packet transmitted from the transmitter B have the samecarrier frequency, the radio signals (packets) of transmitters A and Bcollide with each other. In this way, if collision of wireless signalsoccurs, it is not possible for the receiver to separate packets fromdifferent transmitters, and there is a possibility that an error willoccur in data finally acquired.

For example, in FIG. 5 , it is assumed that the receiver is receiving aradio signal from the transmitter A. Then, one packet among the packetstransmitted from the transmitter A collides with the packet transmittedfrom the transmitter B, and the wireless signal transmitted from thetransmitter B is transmitted from the transmitter A It is assumed thatit is stronger than the radio signal. In this case, the receivercombines the collided packet of the transmitter B as a packet from thetransmitter A. Therefore, there is a possibility that an error occurs inthe synthesized signal and data cannot be extracted. In that case, thereis a possibility that transmission and reception of 10 packets in thesuper frame are all wasted.

In bidirectional communication, it is possible to prompt retransmission,for example, by exchanging necessary information between each of thetransmitters A and B and the receiver. However, in one-waycommunication, it is difficult to supply information from the receivingside to the transmitting side, so it is difficult to takecountermeasures against packet collisions that can be done bybidirectional communication.

FIG. 6 is a diagram showing a configuration example of a positionnotification system which is an embodiment of a wireless system to whichthe present technology is applied. The position notification system 100of FIG. 6 includes transmission devices 101 (101-1 to 101-3), basestations 102 (102-1 and 102-2), a cloud server 103, and an informationprocessing terminal 104. In the position notification system 100, aposition monitoring service for monitoring the position of thetransmitting apparatus 101 is provided by the transmitting apparatus 101performing radio communication with the base station 102 by a newcommunication method.

The transmitting apparatus 101 is an embodiment of a transmittingapparatus to which the present technology is applied, and transmitsposition information indicating the position of itself as a radiosignal. The base station 102 has a receiving device 112. The receivingapparatus 112 is one embodiment of a receiving apparatus to which thepresent technology is applied, receives the radio signal from thetransmitting apparatus 101, acquires the position information of thetransmitting apparatus 101, and transmits the position information andthe like to the cloud server 103. Therefore, the base station 102 havingthe receiving device 112 functions as a relay station that relays theinformation transmitted from the transmitting device 101 and transmitsit to the cloud server 103. The cloud server 103 manages various kindsof information such as the position information of each transmittingapparatus 101, and provides, for example, a service for notifying theuser of the position of the transmitting apparatus 101. For example, theinformation processing terminal 104 operated by a user who wishes toknow the position of the transmitting apparatus 101 accesses the cloudserver 103, acquires the position information of the transmittingapparatus 101, displays it together with, for example, map data, etc.,to the position of the transmission device 101.

The transmitting apparatus 101 carries the object to an object the userwants to monitor, for example, elderly persons or the like. Thetransmitting apparatus 101 has a position sensor that acquires its ownposition information using, for example, GNSS (Global NavigationSatellite System). That is, the transmitting apparatus 101 has, forexample, a receiving mechanism for receiving a GPS signal from a GPS(Global Positioning System) satellite as a position sensor, and obtainsits own position information (for example, latitude and longitude etc.)as appropriate. The transmitting apparatus 101 transmits locationinformation as a radio signal as appropriate.

It should be noted that various types of sensors other than the positionsensor are mounted on the transmission device 101, and the transmissiondevice 101 can transmit the sensor information outputted by the sensorwith a radio signal. For example, a sensor that senses biometricinformation such as a pulse and a heart rate, a sensor that sensestemperature, humidity, etc., a sensor that detects opening and closingof a door, a door, etc., can be mounted on the transmitting device 101.

In FIG. 6 , the transmitting apparatus 101-1 is carried by an elderlyperson 111-1 in Tokyo, the transmitting apparatus 101-2 is carried by anelderly person 111-2 of Yokohama. The transmitting apparatus 101-3 iscarried by an elderly person 111-3 of Shizuoka. Further, thetransmitting apparatus 101 has unique identification information (ID).For example, in FIG. 6 , the identification information of thetransmission device 101-1 is 0001 (ID=0001), the identificationinformation of the transmission device 101-2 is 0002 (ID=0002), theidentification information of the transmission device 101-3 is 0003(ID=0003), respectively. The identification information of thetransmission device 101 is registered in the cloud server 103.

The position monitoring target is arbitrary. For example, the object ofmonitoring the position may be a child, an animal such as a dog or a cat(pet), a company employee, or the like. Although three transmittingapparatuses 101 are shown in FIG. 6 , the number of transmittingapparatuses 101 is arbitrary. The transmission device 101 may beconfigured as a dedicated device, but it may be incorporated in aportable information processing device such as a mobile phone or asmartphone, for example.

The base station 102 may be of any type. For example, the base station102 may be a dedicated facility/building. Further, for example, the basestation 102 may be installed in a roof of a building such as a generalbuilding, an apartment house, a house, a roof or the like. Further, forexample, the base station 102 may be a portable equipment that can becarried by a user or installed in a mobile body such as a car.

A plurality of base stations 102 are installed. For example, in the caseof FIG. 6 , the base station 102-1 is set in Tokyo and the base station102-2 is installed on mount Fuji. Although FIG. 6 shows two basestations 102, the number of base stations 102 is arbitrary.

The base station 102 has a receiving device 112. The receiving device112 receives the radio signal from the transmitting device 101 andprovides information (data) included in the radio signal to the cloudserver 103. Further, the receiving apparatus 112 needs a parameter set(for example, a modulation rate of a wireless signal, on/off offrequency hopping, etc.) as wireless format information for determininga wireless format of wireless communication from the cloud server 103 toget information. The method by which the receiving device 112 acquiresinformation from the cloud server 103 is arbitrary.

The configuration of the cloud server 103 is arbitrary, and may beconstituted by an arbitrary number of servers and an arbitrary number ofnetworks, for example. A plurality of cloud servers 103 may be provided.

In such a position notification system 100, the transmission device 101performs frequency hopping setting based on its own identificationinformation (ID). That is, the transmitting apparatus 101 sets thetransmission timing and the transmission frequency of each packet basedon the identification information and transmits each packet based on thesetting. As described above, by performing transmission using frequencyhopping, the occurrence of interference can be suppressed. That is,information can be more reliably transmitted.

Further, by setting the transmission timing and the transmissionfrequency based on the identification information, the transmissiondevice 101 can change the pattern of the transmission timing and thetransmission frequency for each transmitting apparatus 101. In thiscase, occurrence of collision between packets transmitted from differenttransmission apparatuses 101 can be suppressed. That is, information canbe more reliably transmitted.

In addition, the receiving device 112 of the base station 102 acquiresthe identification information of the transmitting device 101 from thecloud server 103, and performs reception based on the identificationinformation. That is, on the basis of the identification information,the reception device 112 sets reception timing and reception frequencyin the same manner as the transmission timing and transmission frequencysetting of the transmission device 101. If the transmission timing andthe transmission frequency of the packet can be specified by theidentification information of the transmission device 101 in thereception device 112, it suffices to detect the packet with respect tothe transmission timing and the transmission frequency (that is, thereception timing and the reception frequency are changed So that it iseasier to detect packets even when the S/N ratio is low. Therefore,reception with higher sensitivity becomes possible. That is, morereliable transmission of information can be realized. In addition, it isnot necessary to perform processing such as packet detection inunnecessary timing and unnecessary frequency band, so it is possible tosuppress an increase in load.

In addition, priority can be attached to the identification informationof the transmission device 101. In the case where the priority isattached to the identification information of the transmission device101 acquired from the cloud server 103, the reception device 112selects, in accordance with the priority of the identificationinformation, the radio wave from the transmission device 101 identifiedby the identification information It is possible to receive a signal(packet). In this case, more reliable transmission of information can berealized.

It is to be noted that the receiving device 112 transmits information onthe reception of the radio signal, for example, when and when the radiosignal from the transmitting device 101 is received, the content of theradio signal (data extracted from the radio signal) to the server 103.

The cloud server 103 preliminarily registers and manages information(also referred to as terminal information) about the transmitting device101 and information about the user (also called subscriber information).The terminal information may include, for example, identificationinformation of the transmission device 101, information of transmissionfrequency, main location, and the like. Further, the subscriberinformation can include, for example, the name, age, gender, address,payment information of the user (person receiving the positionnotification service), identification information of the transmittingapparatus to be used, login ID, password, and the like. Of course, theterminal information and the subscriber information may each include anyinformation, and the present disclosure is not limited to the aboveexample.

Further, the cloud server 103 transmits the identification informationof the transmitting apparatus 101 to the receiving apparatuses 112 ofthe base stations 102 (some or all of the base stations 102) at apredetermined timing or in response to a request from the receivingapparatus 112 or the like. At that time, the cloud server 103 can supplythe base station 102 with the identification information of thetransmitting device 101, which is highly likely to receive the radiosignal by the base station 102. In other words, the cloud server 103cannot supply the base station 102 with the identification informationof the transmitting apparatus 101, which is less likely to receive theradio signal by the base station 102. By doing so, it is possible toreduce the detection of unnecessary packets in the receiving apparatus112 of the base station 102, and it is possible to suppress an increasein the load.

Also, as the number of transmitting apparatuses 101 to be received bythe base station 102 increases, the probability that packet collisionoccurs increases accordingly. More precisely, since there is a lowpossibility that a packet will arrive from the transmitting device 101,which is unlikely to receive a radio signal, the probability that packetcollision will actually occur will not be high. However, in setting thereception timing and the reception frequency performed in the basestation 102, the probability that packet collision occurs increases asthe number of target transmission apparatuses 101 increases. Asdescribed above, when packet collision occurs in the setting of thereception timing and the reception frequency, the reception of thepacket is omitted. Therefore, if the receiving apparatus targets thetransmitting apparatus 101, which is less likely to receive a radiosignal, the receiving sensitivity unnecessarily decreases, and thereliability of information transmission may unnecessarily be reduced. Asdescribed above, the cloud server 103 does not supply the identificationinformation of the transmission device 101, the possibility of which thebase station 102 is less likely to receive the radio signal, so that thebase station 102 transmits such a transmission device 101 as a receptiontarget. In this case, it is possible to suppress the reduction in thereception sensitivity and achieve more reliable informationtransmission.

Further, the cloud server 103 acquires reception information obtained byreceiving the radio signal from the reception device 112 of the basestation 102. Based on the received information, for example, the cloudserver 103 records the history of transmission/reception of informationbetween the transmission device 101 and the reception device 112 (forexample, the radio signal transmitted from which transmission device 101is transmitted to the base station 102 When the receiving device 112received it, etc.). Based on this history, the cloud server 103 selectsthe transmission device 101 that supplies the identification informationto the base station 102, and in accordance with the selection result,the cloud server 103 transmits the identification information (LEID(List of Expected ID)) and supplies it to the receiving device 112 ofthe station 102. In this way, by supplying the identificationinformation of the transmission device 101 to the reception device 112of each base station 102 based on the past communication history, thereception device 112 of each base station 102 transmits the radio signalof each transmission device 101 can be more accurately determined.Therefore, each base station 102 can realize more reliable transmissionof information.

Further, the cloud server 103 can provide, for example, the position ofthe transmission device 101 (elderly person 111) to the informationprocessing terminal 104 based on the reception information from thereception device 112.

It should be noted that the identification information of thetransmission device 101 may be supplied from the cloud server 103 to thebase station 102 in any form. For example, the cloud server 103 maysupply the identification information of the transmission device 101 tothe base station 102 as a priority list. This priority list isinformation including a list of identification information of thetransmission device 101 which is highly likely to receive a radio signalby the base station 102 to which the priority list is supplied. Forexample, the cloud server 103 generates and supplies a priority list forthe base station 102 to each base station 102, and the base station 102that has been supplied with the priority list transmits a transmissionin which identification information is indicated in the priority list.Processing may be performed so as to receive a radio signal from theapparatus 101. In addition, the reception priority of the base station102 may be added to the identification information of the transmissiondevice 101 supplied to the base station 102. For example, the abovepriority list may include the priority of each identificationinformation. Then, the base station 102 supplied with the priority listmay set the priority order of signal reception, etc. based on thepriority included in the priority list. By doing so, the cloud server103 can not only control the transmitting apparatus 101 that the basestation 102 receives the radio signal, but also can control the priorityorder of the reception. It is also possible to obtain the communicationdistance from the difference between the position where the base station102 exists and the position information transmitted by the transmissiondevice 101 and change the priority according to this communicationdistance.

FIG. 7 is a block diagram showing a configuration example of thetransmission apparatus 101. The transmitting apparatus 101 includes aGPS signal receiving section 201, a payload data generating section 202,an ID/CRC adding section 203, an FEC processing section 204, a repeatingsection 205, a guard bit adding section 206, a key stream generatingsection 211, an AND gate 212, an EXOR A gate 213, a Gold code generationunit 214, an EXOR gate 215, a sync generation unit 221, an interleaveunit 222, a modulation unit 223, and a frequency/timing control unit224. In some embodiments only single or a selected number of theelements 206-224 may be provided and may be commonly referred to astransmission section.

The GPS signal receiving unit 201 receives the GPS signal, acquires a 1PPS (pulse/second) signal and the current time (GPS time) included inthe GPS signal, and supplies it to the frequency/timing control unit 224as a clock signal. In addition, the GPS signal receiving unit 201acquires the position information (latitude, longitude, altitude) of thetransmitting apparatus 101 from the GPS signal and supplies the positionto the payload data generating unit 202 as the sensed sensorinformation.

The payload data generation unit 202 generates payload data to be apayload of the radio signal from position information serving as sensorinformation from the GPS signal reception unit 201, and supplies thepayload data to the ID/CRC attachment unit 203. Note that theinformation to be the payload data is not limited to the positioninformation and further the sensor information. The information to bethe payload data can be decided according to, for example, anapplication to which the wireless system is applied or the like.However, the new communication method is a kind of a new communicationmethod for LPWA communication which can transmit information in a widerange of several 10 to 100 km with low power consumption, and the sizeof the information serving as the payload data is suitable for LPWAcommunication It is desirable to have a size.

The ID/CRC attachment unit 203 adds an ID (identification information)of the transmission device 101 and a CRC (Cyclic Redundancy Check) codeto the payload data from the payload data generation unit 202 to therebyperform FEC (Forward Error Correction) generates an FEC target unit tobe processed, and supplies it to the FEC processing unit 204. The ID/CRCattachment unit 203 generates a CRC code for payload data or payloaddata and ID.

The FEC processing unit (also called FEC encoder) 204 performs FECprocessing on the FEC target unit from the ID/CRC attaching unit 203,and supplies the FEC frame obtained as a result to the repeating unit205. That is, the FEC processing unit 204 performs error correctioncoding of the FEC target unit as FEC processing of the FEC target unit,and supplies the error correction code obtained by the error correctioncoding to the repeating unit 205. Specifically, in an embodiment the FECprocessing unit 204 performs, for example, LDPC encoding of the FECtarget unit and supplies the LDPC code obtained by the LDPC encoding tothe repeating unit 205. It should be noted that the error correctioncode is not limited to the LDPC code. As the error correction code, forexample, a convolutional code, a turbo code, or the like can be adopted.

The repeating unit 205 (also called frame forming section or including aframe forming section) generates a repeating unit in which the LDPCcodes from the FEC processing unit 204 are repetitively arranged, andsupplies it to the guard bit adding unit 206. The repeating unit 205employs aspects of the present disclosure and will be explained in moredetail below.

The guard bit adding section 206 adds (inserts) a guard bit to therepeating unit from the repeating unit 205 and supplies it to the EXORgate 213.

The key stream generating unit 211 generates a key stream to be used forencryption and supplies it to the AND gate 212. In addition to the keystream from the keystream generating unit 211, a switching signal forswitching the validity/invalidity of encryption in the EXOR gate 213 issupplied to the AND gate 212.

The switching signal is, for example, a logical 1 (for example, Highlevel) in the case of encryption being enabled, and a logical 0 (forexample, Low level) in the case of invalidating the encryption. Theswitching signal can be set, for example, according to the application.The switching signal can be set so that the whole of the repeating unitsupplied from the guard bit adding unit 206 to the EXOR gate 213 or apart of the repeating unit is validly encrypted. Further, the switchingsignal can be set so that the entire encryption of the repeating unitsupplied from the guard bit adding unit 206 to the EXOR gate 213 isinvalidated.

The AND gate 212 calculates the logical product of the switching signaland the key stream from the keystream generating unit 211, and suppliesit to the EXOR gate 213. As a result, the key stream is supplied fromthe AND gate 212 to the EXOR gate 213 only during the period in whichencryption is effective in the switching signal.

The EXOR gate 213 encrypts the repeating unit with the stream cipher(method) by computing the exclusive OR of the repeating unit from thecard bit adding section 206 and the key stream from the AND gate 212.The EXOR gate 213 supplies the encrypted repeating unit to the EXOR gate215. Here, in the EXOR gate 213, the period during which the keystreamfrom the AND gate 212 is supplied, that is, the period during which theswitching signal is at logic 1 is encrypted. Therefore, in the EXOR gate213, all or a part of the repeating unit may be encrypted, or the entirerepeating unit may not be encrypted. For example, the Gold codegenerating unit 214 generates, for example, a Gold code as a scramblingsequence of the same size (number of bits) as that of the repeating unitfrom the EXOR gate 213, using two M sequence generators, and the EXORgate 215. The EXOR gate 215 scrambles the repeating unit by computingthe exclusive OR of the repeating unit from the EXOR gate 213 and thescrambling sequence from the Gold code generating unit 214, and suppliesit to the interleaving unit 222.

The sync generation unit 221 generates a predetermined PN (Pseudo Noise)sequence such as M sequence, for example, as a synchronization signal,and supplies it to the interleave unit 222. It should be noted that thesynchronization signal generated by the sync generation unit 221 is aknown signal by the transmission device 101 and the reception device112. Since the synchronization signal is known by the transmissiondevice 101 and the reception device 112, the reception device 112 canperform synchronous detection of the radio signal from the transmissiondevice 101, robust reception of the radio signal from the transmissiondevice 101 can do. The initial value of the M sequence may be any valueas long as it is a common value for transmission and reception. It isalso possible to change the initial value of the M sequence according tothe ID.

The interleave section 222 performs bit sequence d(0), d(1), . . . . Asa repeating unit from the EXOR gate 213 and bit sequences r(0), r(1), .. . and interleaved sequences r(0), d(0), r(1), d(1), . . . , or r0 (0),d(0), d(832), r(1), d(1), . . . to the modulation section 223.

The modulation unit 223 performs modulation such as π/2 shift BPSK (π/2Shift Binary Phase Shift Keying) modulation and chirp modulation using,for example, the interleave sequence supplied from the interleaving unit222, For example, a 920 MHz band radio signal as a modulated signalobtained by the above-described method. Note that the modulation unit223 transmits the radio signal at the transmission timing and thetransmission frequency according to the control from thefrequency/timing control unit 224.

The frequency/timing control unit 224 sets the transmission timing andthe transmission frequency of the wireless signal transmitted by themodulation unit 223 according to the ID or the like of the transmissiondevice 101, and transmits the wireless signal at the transmission timingand the transmission frequency, and controls the modulation section 223.The frequency/timing control unit 224 controls the modulation unit 223in synchronization with the clock signal from the GPS signal receptionunit 201. That is, in accordance with the clock signal from the GPSsignal receiving unit 201, for example, the frequency/timing controlunit 224 determines whether or not the current timing is a grid which isknown (predetermined timing) in the transmission device 101 and thereception device 112. It recognizes whether it is timing (grid time),and controls the modulation unit 223 so that transmission of packets isstarted at grid timing.

FIG. 8 is a block diagram showing a configuration example of thereception device 112. The reception device 112 includes a GPS signalreception unit 231 (or generally a receiving section), anID/transmission pattern acquisition unit 232, a frequency/timing controlunit 233, a demodulation unit 234 (representing and/or including a frameextraction section), and a decoding unit 235 (representing the FECdecoder).

The GPS signal receiving unit 231 receives the GPS signal, acquires 1PPS signal and GPS time included in the GPS signal, and supplies it tothe frequency/timing control unit 233 as a clock signal. For example,from the cloud server 103, the ID/transmission pattern acquiring unit232 acquires a transmission pattern that is a pattern of the ID of thetransmission device 101, the transmission timing, and the transmissionfrequency that the reception device 112 receives as a reception targetof the radio signal from the timing control unit 233.

The frequency/timing control unit 233 sets the reception timing and thereception frequency of the radio signal in the demodulation unit 234according to the transmission pattern from the ID/transmission patternacquisition unit 232, and receives the radio signal at the receptiontiming and reception frequency so as to control the demodulation unit234. As with the frequency timing control unit 224 in FIG. 7 , thefrequency/timing control unit 233 controls the demodulation unit 234 insynchronization with the clock signal from the GPS signal reception unit231.

As described above, both of the transmission timing and the transmissionfrequency control of the modulation section 223 (FIG. 7 ) and thereception timing and the reception frequency control of the demodulationsection 234 are controlled by the clock signal obtained from the GPSsignal and By synchronizing with the time information, it is possible toprecisely match the transmission timing and the transmission frequencyof the modulation section 223 with the reception timing and receptionfrequency of the demodulation section 234.

The demodulation unit 234 receives the radio signal from thetransmission device 101 at the reception timing and reception frequencyaccording to the control of the frequency/timing control unit 233,performs FFT (Fast Fourier Transform) etc. of the radio signal anddemodulates the radio signal. The demodulation unit 234 supplies thedemodulation signal obtained by demodulating the radio signal to thedecoding unit 235. In the demodulation of the decoding unit 234, forexample, synchronous detection using a synchronization signal isperformed, and the combination described in FIG. 2 is also performed.

The decoding unit 235 performs error correction by decoding the LDPCcode included in the decoded signal from the demodulation unit 234 andoutputs the sensor information included in the payload data obtained asa result. This sensor information is transmitted from the receivingdevice 112 to the cloud server 103.

FIG. 9 is a diagram showing an example of a first format of data(signal) handled by the transmission apparatus 101. Here, in the newcommunication method, there are two modulation rates (transmissionrates) of 6.35 kbps and 50.8 kbps, for example, which are performed inthe modulation section 223. FIG. 9 shows the format of data when themodulation rate is 6.35 kbps out of 6.35 kbps and 50.8 kbps.

In the new communication method, three types of modes, i.e., MSDUType-1, MSDU Type-2, and MSDU Type-3, are prepared as payload datasetting modes, for example. The payload data is, for example, a 128-bitunit called MSDU (MAC (Media Access Control) Service Data Unit). In thecase of MSDU Type-1, MSDU Type-2, MSDU Type-3, the actual data length is128 bits, 64 bits, or 1 bit respectively. It is used for transmission ofdata (user data). That is, in MSDU Type-1, the payload data generationunit 202 uses 128-bit actual data (sensor information etc.) as it is toconstruct (generate) a 128-bit MSDU Service Data Unit. In MSDU Type-2,the payload data generation unit 202 pads 64-bit real data with 64 bitsof 0 to form a 128-bit MSDU. In MSDU Type-3, the payload data generationunit 202 pads 1-bit actual data with 127 bits of 0 to form a 128-bitMSDU.

The MSDU Type depends on the application. E.g. transmission oflocalization data may require 128 bits (Type-1), while other sensors mayonly transmit less information. For binary sensor data (on/off,true/false), one data bit is sufficient (Type-3), e.g., for earlyearthquake detectors. In general, the actual data length may be anarbitrary number smaller or equal than a predetermined maximum, e.g., upto 128 bits. The MSDU Type index is e.g. stored together with the deviceID (userID) on a cloud server, so that the receiver knows about theactual data length.

In the 128-bit MSDU, the 32-bit ID of the transmitting apparatus 101 andthe 24-bit CRC code are added in the ID/CRC attaching section 203,whereby PSDU (Physical Layer Service Unit) as the FEC target unit and itbecomes a unit of 184 bits.

In the FEC processing unit 204, for example, the 184-bit PSDU is codedinto an LDPC code having a code length N of 736 bits and a coding rate rof 1/4, resulting in 736 bits (=184×4/1) LDPC code (encoded bit).

In the first format where the modulation rate is 6.35 kbps, the LDPCcode of 736 bits is repeated twice, and further, 184 bits of a part ofthe LDPC code of 736 bits are repeated to generate 1656 bits (=736bits×2+184 bits) repeating unit. That is, in the first format, therepeat unit is configured by arranging a 736-bit LDPC code repeatedlytwice and further arranging a part of 184 bits of the 736-bit LDPC code.

As the 184 bits of a part of the 736-bit LDPC code arranged in therepeating unit, for example, the first 184 bits of the 736-bit LDPC codecan be adopted. Also, 184 bits of a part of the 736-bit LDPC codearranged in the repeat unit can be selected according to a predeterminedoptimization pattern, according the present disclosure. To the repeatingunit, a guard bit is added (inserted) by the guard bit adding unit 206.That is, a 4-bit guard bit (G) is added to each of the head and the endof the repeating unit. By the addition of the guard bit, the repeatingunit of 1656 bits becomes a repeating unit of 1664 bits (=1656 bits+4bits×2). As the 4-bit guard bits, for example, all 0 bits can be adoptedor a counter indicating the frame number.

Here, in the FFT of the repeating unit performed in the demodulatingunit 234 (FIG. 8 ) of the receiving apparatus 112, the signal quality atthe end of the repeating unit is deteriorated. As a countermeasureagainst deterioration of the signal quality, guard bits are added to thehead and the end of the repeating unit, respectively. For the repeatingunit, the EXOR gate 213 calculates an exclusive OR with the keystream,whereby the repeating unit becomes an encrypted stream.

Here, when the setting mode of the payload data is MSDU Type-2 or MSDUType-3, a part of the 128-bit MSDU as payload data is padded 0. SinceMSDU Type-2 pads 64-bit real data with 64 bits of 0, half of the 128-bitMSDU is 0. In other words, half of the MSDU is meaningless information.In MSDU Type-3, since 1-bit real data is padded with 127 bits of 0, mostof the 128-bit MSDU is meaningless information.

In the new communication method, in the case where there are many suchmeaningless information (in the case of MSDU Type 2 or MSDU Type 3), itis configured so that the wireless energy sent out to the communicationpath can be maximally and effectively utilized. That is, in the newcommunication method, data generated as padding 0 (part or all) cannotbe encrypted. When padding 0 is not to be encrypted, the AND gate 212 issupplied with a switching signal for invalidating the encryption of thepadding period 0 in the repeating unit. In response to the switchingsignal, the AND gate 212 supplies the key stream to the EXOR gate 213,whereby the EXOR gate 213 in the EXOR gate 213 generates a key stream ina period in which encryption is not ineffective, that is, a period inwhich encryption is valid. The repeat unit is encrypted using the keystream from the AND gate 212 as a target. In the portion whereencryption is ineffective, padding 0 data is output as it is withoutbeing encrypted. It is known that the portion of the encryptioninvalidated in this way is data 0 in the receiving device 112.Therefore, in the demodulation unit 234 of the reception apparatus 112,it is possible to improve the synchronization performance by treatingthe signal of the portion where the encryption is invalid as thesynchronization signal. Likewise, in the demodulation section 235, theerror correction performance can be improved by decoding the portion inwhich encryption is invalidated as known data “0”. That is, by partiallyinvalidating the encryption when the payload is short, the performanceof the receiving device 112 is improved. By such performanceimprovement, it is possible to realize equivalent communicationperformance even with lower transmission antenna power, for example.

Like the repeating unit before encryption, the encrypted stream iscomposed of 1664 bits. The 1664 bit encrypted stream is scrambled byexclusive OR with the gold code as the scrambling sequence by the EXORgate 215, and becomes a scrambled stream. The scrambled stream is a1664-bit bit sequence d(0), d(1), . . . , d(1663) similarly to thecipher stream before scrambling.

For the first format in which the modulation rate is 6.35 kbps, the sinkgeneration unit 221 generates bit sequences r(0), r(1), . . . r(831) as832-bit synchronization signals (Sync)). Therefore, for the first formatwith a modulation rate of 6.35 kbps, the ratio of the length of the syncsignal to the length of the scrambled stream is 832:1664=1:2.

A bit series r(0), r(1), . . . r(831) as a synchronizing signal of 832bits and bit series d(0), d(1), . . . as a 1664 bit scramble stream,d(1663) are interleaved in the interleave section 222. As a result, bitsequences r(0), d(0), d(832), r(1), d(0), d(0), d(0), d(2), and so on)as 2496 bits PPDU (Presentation Protocol Data Unit) (1), d(833) . . .are generated.

Here, bit sequences r(0), r(1), . . . , r(831) as 832-bitsynchronization signals and bit sequences d(0), d(1) as 1664-, . . . ,d(1663) are interleaved, for example, in accordance with the following Cprogram. Note that PPDU (n) represents the (n+1) th bit from the head ofthe 2496 bit PPDU, and (n % x) represents the remainder obtained bydividing n by x. The symbol “==” means to judge whether the calculationresult is equal or not. Also, in the division calculation (n/3 etc.)where n is a dividend, decimals below the decimal point are truncated:

For (n = 0; n <2496; n ++) {  If ((n% 3) == 0) PPDU (n) = r (n / 3);  If((n% 3) == 1) PPDU (n) = d (n / 3);  If ((n% 3) == 2) PPDU (n) = d (n /3 + 1); }

For the 2496-bit PPDU, π/2 shift BPSK modulation of 6.35 kbps isperformed by the modulator 223, and chirp modulation of 400 kHz/s isfurther performed. Then, the 2496 bit PPDU is transmitted as a radiosignal.

For a 2496 bit PPDU, when π/2 shift BPSK modulation at 6.35 kbps isapplied, the transmission (transmission) time of the 2496 bit PPDU isabout 393.2 ms. It is a transmission of 0.4 seconds or less andsatisfies the ARIB regulation of the 920 MHz band.

For chirp modulation, for example, a frequency shift of about −78.6 kHzis given at the start of transmission of a PPDU with a transmission timeof about 393.2 ms. With chirp modulation at 400 kHz/s, the frequencylinearly changes at a change rate of 400 kHz/s, so the frequency shiftat the end of transmission of the PPDU with a transmission time ofapproximately 393.2 ms is approximately +78.6 kHz. For example, when thefrequency (center frequency) of the carrier is 925 MHz, the signalfrequency of the radio signal changes linearly from 924.9214 MHz to925.0786 MHz by chirp modulation. With this chirp modulation, even if amodulation rate of 6.35 Kbps is used, since frequency utilizationefficiency improves, it becomes strong against interference and also itis possible to reduce the amount of calculation involved insynchronization detection due to the characteristics of chirpmodulation.

For the first format, the transmitting apparatus 101 repeatedlytransmits the PPDU as a packet, for example, four times. In this case,the time required for four transmissions of the PPDU is about 1.57seconds (=393.2 ms×4).

In the present embodiment, one type of LDPC code having a code length Nof 736 bits and a coding rate r of 1/4 is prepared as the LDPC code,while setting mode of the payload data is MSDU Type 1, MSDU Type-2, andMSDU Type-3, padding of 0 constitutes an 184-bit PSDU as an FEC targetunit, LDPC encoding of the 184-bit PSDU is classified into one type LDPCcodes for respective setting modes are prepared for each setting mode,for example, LDPC coding of real data in each setting mode is performedwithout padding of 0, can be performed using the LDPC code for thesetting mode.

However, when preparing an LDPC code for each setting mode, it isnecessary for the transmitting apparatus 101 to store the check matrixof the LDPC code for each setting mode, and in the LDPC encoding,processing such as switching matrices is required. On the other hand,when one type of LDPC code having a code length N of 736 bits and acoding rater of 1/4 is used in the transmitting apparatus 101, as forthe LDPC code, a check matrix of one type of LDPC code is stored and itis not necessary to switch the check matrix, so that it is possible toreduce the load and consequently reduce the power consumption.

FIG. 10 is a diagram showing an example of a second format of datahandled by the transmitting apparatus 101. That is, FIG. 10 shows theformat of data when the modulation rate is 50.8 kbps out of 6.35 kbpsand 50.8 kbps.

In the second format, the MSDU as the payload data, the PSDU as the FECtarget unit, and the LDPC encoding are the same as in the case of thefirst format (FIG. 9 ), so the description is omitted. In the secondformat where the modulation rate is 50.8 kbps, the LDPC code of 736 bitsis repeated six times and further 384 bits of the LDPC code of 736 bitsare repeated so that 4800 bits (=736 bits×6+384 bits) repeating unit.That is, in the second format, the repeating unit is configured byarranging a 736-bit LDPC code repeatedly six times and further arranging384 bits of a part of the 736-bit LDPC code.

As the 384 bits of a part of the 736-bit LDPC code arranged in therepeating unit, for example, the first 384 bits of the LDPC code of 736bits can be adopted. Also, 384 bits of a part of the 736-bit LDPC codearranged in the repeat unit can be selected according to a predeterminedoptimization pattern, according this disclosure.

For the repeating unit, as in the case of the first format, a 4-bitguard bit (G) is added to the head and the end, respectively. By theaddition of the guard bit, the repeating unit of 4800 bits becomes arepeating unit of 4808 bits (=4800 bits+4 bits×2). Thereafter, in thesecond format, as in the case of the first format, a 4808 bit repeatingunit is encrypted to be an encrypted stream, further scrambled, and madeinto a scrambled stream. In the second format, the scrambled stream is a4808 bit sequence of bits d(0), d(1), . . . , d(4807) of the same sizeas the repeating unit to which the guard bit is added.

As for the second format, the sink generation unit 221 generates bitsequences r(0), r(1), . . . r(0), . . . , r (0) as a 4808 bitsynchronization signal (Sync) of the same size as the scramble stream4087. Therefore, for the second format, the ratio of the length of thesynchronizing signal to the length of the scrambled stream is4808:4808=1:1.

A bit sequence r(0), r(1), . . . r(4087) as a 4808 bit synchronizationsignal and bit sequences d(0), d(1), . . . as a 4808 bit scramblestream, and d(4807) are interleaved by the interleave section 222. As aresult, bit sequences r(0), d(0), r(1), d(1), and d(0) as PPDUs of 9616bits (=4808 bits+4808 bits), in which bits as synchronization signalsare periodically inserted, . . . are generated. Here, the bit seriesr(0), r(1), . . . , r(4807) as 4808 bit synchronization signals and thebit series d(0), d(1) as 4808 bit scramble streams, . . . , d(4807) areinterleaved according to the following C program, for example:

For (n = 0; n <9616; n ++) {  If ((n% 2) == 0) PPDU (n) = r (n / 2);  If((n% 2) == 1) PPDU (n) = d (n / 2); }

For the 9616 bit PPDU, π/2 shift BPSK modulation of 50.8 kbps isperformed by the modulating unit 223, and it is transmitted as a radiosignal. When π/2 shift BPSK modulation of 50.8 kbps is applied to the9616 bit PPDU, the transmission time of the 9616 bit PPDU is about 189.4ms. Since it is less than the ARIB prescribed 0.2 seconds, it becomespossible to send it repeatedly a plurality of times with a shorttransmission pause time.

Regarding the second format, the transmitting apparatus 101 repeatedlytransmits the PPDU as a packet, for example, 20 times. In this case, thetime required for transmitting 20 PPDUs is about 3.78 seconds (=189.4ms×20). In the second format, since the number of times of repetition islarge, even if there is an influence such as fading, information can bemore reliably transmitted.

Selection of the first format and the second format has different fadingcharacteristics and the like required by the application, so it may beselected by the application.

In FIG. 11 , the key stream generation unit 211 includes a keygeneration unit 251, a Nonce generation unit 252, a block encryptionunit 253, and a P/S conversion unit 254. The key stream generating unit211 generates a key stream used for encryption. For the first format,the key stream generating unit 211 generates a 1664 bit key stream, andfor the second format, a 4808 bit key stream is generated.

The key generation unit 251 generates 128-bit key information. Withregard to the key generation unit 251, the internal structure is madeundisclosed, and the security of encryption is secured. Regarding thekey generation unit 251, as long as the internal structure cannot beeasily guessed, its configuration may be any configuration. For example,the key generation unit 251 may obtain (generate) key information byacquiring the GPS time from the GPS signal reception unit 201 (FIG. 7 )and adding zero data so that the number of bits becomes 128 bits it can.The key generation unit 251 supplies the generated key information tothe block encryption unit 253.

The Nonce generation unit 252 generates 128 bit Nonce (Number usedONCE). As for Nonce, it is expected that the value will be differenteach time the bit clock is divided by 128. For example, the Noncegenerating unit 252 can be constituted by a 128-bit counter. In thiscase, for example, the Nonce generation unit 252 initializes the counterto a predetermined count value before starting the transmission of thewireless signal, and thereafter increments the count value by 1 at eachtiming when the bit clock is divided by 128 By doing so, Nonce can begenerated. The Nonce generation unit 252 supplies the generated Nonce tothe block encryption unit 253.

The block encryption unit 253 generates a 128-bit block cipher using thekey information from the key generation unit 251 and Nonce from theNonce generation unit 252, and supplies the block cipher to the P/Sconversion unit 254. As the block cipher, for example, an AES (AdvancedEncryption Standard) code, a CLEFIA code, or the like can be used.

The P/S converter 164 performs P/S (Parallel to Serial) conversion onthe block cipher in units of 128 bits from the block encrypting unit 253in units of 1 bit to generate a key stream in serial (1 bit unit) Andsupplies it to the AND gate 212. For the first format, the P/S converter164 generates a 1664-bit key stream, and for the second format, itgenerates a 4808-bit key stream.

According to the present disclosure the FEC encoder 204 is configured toencode payload data into FEC code words 300, 400 (see FIGS. 9 and 10 )each having a predetermined code word length. The frame forming section(represented by or included in the repeating unit 205) is configured toform a frame 310, 410 having a predetermined frame length. Atransmission stream 320, 420 is then formed from a plurality of frames310, 410 formed by said frame forming section. This will be explained inmore detail in the following.

A frame 310 is separately shown in FIG. 12 , a frame 410 is separatelyshown in FIG. 13 . As shown in these figures, a frame 310, 410 comprisesa first frame portion 311, 411 having a first predetermined length of aninteger multiple of the predetermined code word length and a secondframe portion 312, 412 having a second predetermined length shorter thanthe predetermined code word length. Further, in this exemplaryembodiment a third frame portion 313, 413 and a fourth frame portion314, 414 each comprises guard bits are provided; in other embodiments,however, no such third and fourth frame portions, or one or more furtherframe portions are provided in addition to the first and second frameportions. The guard bits can e.g. provide information about the framenumber inside the superframe, e.g., guard bits are 0000 for the firstframe, 0001 for the second frame, and so on (repeated at both beginningand end of the frame 310, 410).

The frame 310 is preferably used for format1 from FIG. 9 (6.35K Chirp),whereas frame 410 is preferably used for format2 from FIG. 10 (50.8KDSSS). The 50.8K mode uses an 8 times larger bandwidth, which willresult in 8 times more noise power in an additive white Gaussian noise(AWGN) channel. Thus, more repetitions of FEC code words 400 are used (6times), compared with only 2 FEC codeword repetitions in case offormat1. One way to completely compensate for the larger noise level inthe format2 case is to use exactly 8 times more FEC code words 400.Another way is to increase only partly the FEC code word number, andfurther increase the number of transmitted frames 410 in addition.

The frame forming section is further configured to include an FEC codeword 300, 400 and a predetermined number of repetitions of said FEC codeword 300, 400 into the first frame portion 311, 411 of a frame and toinclude a selected number of bits of said FEC code word 300, 400 intothe second frame portion 312, 412 of said frame. As shown in FIG. 12 ,the first frame portion 311 comprises two repetitions of the code word300. As shown in FIG. 13 , the first frame portion 411 comprises tworepetitions of the code word 400.

FIGS. 14A to 14H and 15A to 15I show a code word 300 and 400,respectively, and various options which part of the code word 300, 400to include in the second frame portion 312, 412. In these exemplaryembodiments the code word 300, 400 is a code word of a systematic code,in particular of an LDPC code, and comprises, as shown in FIGS. 14A and15A, an information portion 315, 415 of 184 information bits and aparity portion 316, 415 of 552 parity bits, totaling 736 code bits. Inother embodiments, however, other codes and other numbers of bits may beapplied.

FIG. 14B to 14H show seven different options for including a part of thecode word 300 in the second frame portion 312 of the frame 310. Thispart is indicated in these figures by a separate hatching. In thisembodiment, which refers to the embodiment shown in FIG. 9 and FIG. 12 ,the second frame portion 312 comprises 184 bits.

According to a first pattern (called pattern 0) shown in FIG. 14B onlyinformation bits, in particular the complete information portion 315,are included in the second frame portion 312. This provides that theinformation bits are protected more strongly.

The FEC code can be an instance of a low-density parity-check (LDPC)code, with optimized degree spectrum to allow decoding at very low SNR.In a preferred embodiment, the LDPC code is systematic and uses adual-diagonal line in the parity part of the parity-check matrix (i.e.,systematic code, and parities will be accumulated). This results inparities having variable degree of 2 (only 2 outgoing edges, i.e.,connections, to check nodes). This affects 551 parities out of 552parity bits. The very last parity bit has only degree 1. The informationbits, however, use larger degrees, e.g., degrees 10, 9, and—in part—3.The overall degree spectrum was subject to code optimization. It shouldbe noted that code bits with small variable node degree collect onlylimited amount of information during message-passing decoding at FECdecoder. Thus, it is beneficial to repeat parities of the LDPC codeword, since they have smaller variable node degree.

According to a second pattern (called pattern 1) shown in FIG. 14C onlyparity bits, in particular the 184 least significant parity (defined asthe rightmost bits of the bit sequence) bits 317 of the parity portion316, are included in the second frame portion 312. This provides thatweak parities are protected more strongly and thus improves codeconvergence and is simple for implementation However, the aggregation ofstronger parity bits is very local in the FEC code word and may notallow the FEC decoder to converge to low bit error rates.

According to a third and fourth pattern (called patterns 2 and 3) shownin FIGS. 14D and 14E evenly spread code bits 318, including informationbits and parity bits, of all code bits of the code word 300 are includedin the second frame portion 312. This provides that separately protectedbits are evenly spread over the complete code word, which may bebeneficial for codes having an equal error protection (EEP) among allcode bits. In a preferred embodiment, an irregular LDPC code is used,where code bits have unequal error protection (UEP), with the first codebits being more robust compared to the last (parity) bits.

According to a fifth, sixth and seventh pattern (called patterns 4, 5and 6) shown in FIG. 14F, 14G, 14H only parity bits, in particularparity bits 318 evenly spread over the parity portion 316, are includedin the second frame portion 312. This provides that these parity bits319 are protected more strongly. It is noted that for patterns 5 and 6only a triple 320 of parity bits is shown to indicate the different waysof evenly spreading the parity bits 319 to be protected. These patterns(4, 5, and 6) are simple to implement (regular structure) and allow forevenly distributed parity repetition. This results in the overall bestFEC decoding performance.

FIG. 15B to 15H show seven different options for including a part of thecode word 400 in the second frame portion 412 of the frame 410. Thispart is indicated in these figures by a separate hatching. In thisembodiment, which refers to the embodiment shown in FIG. 10 and FIG. 13, the second frame portion 412 comprises 384 bits.

According to a first pattern (called pattern 0) shown in FIG. 15Binformation bits, in particular the complete information portion 415,and the most significant (defined as the leftmost bits of the bitsequence) (200) parity bits 423 are included in the second frame portion412. This provides that the information bits are protected morestrongly.

According to a second pattern (called pattern 1) shown in FIG. 15C onlyparity bits, in particular the 352 least significant parity bits(defined as the rightmost bits of the bit sequence) 417 of the parityportion 416, are included in the second frame portion 412. This providesthat weak parities are protected more strongly and thus improves codeconvergence.

According to a third and fourth pattern (called patterns 2 and 3) shownin FIGS. 15D and 15E evenly spread code bits 418, including informationbits and parity bits, of all code bits of the code word 400 are includedin the second frame portion 412. Further, a longer portion 421 of (here32) code bits from the beginning or end of the code word 400 is includedin the second frame portion 412. This provides that separately protectedbits and the longer portion 421 are evenly spread over the complete codeword, with small exceptions at the beginning and the end of the codeword, where a block of 32 bits is repeated.

According to a fifth, sixth and seventh pattern (called patterns 4, 5and 6) shown in FIG. 15F, 15G, 15H only parity bits, in particularparity bits 419 evenly spread over the parity portion 416, are includedin the second frame portion 412. Further, also in these embodiments alonger portion 422 of (here 48) parity bits from the end of the parityportion 416 is included in the second frame portion 412. This providesthat these parity bits 419 and 422 are protected more strongly. It isnoted that for patterns 5 and 6 only a triple 420 of parity bits isshown to indicate the different ways of evenly spreading the parity bits419 to be protected.

According to an eighth pattern (called pattern 7) shown in FIG. 15I the384 repeated bits 424 are evenly distributed over the parity portion 416with a completely regular pattern (called pattern_23) without repeatinga large block towards the end of the codeword (as in patterns 4, 5 and6). This is simple to implement (regular structure) and allows forevenly distributed parity repetition. This results in the overall bestFEC decoding performance.

A receiving apparatus according to the present disclosure generallycomprises a frame extraction section that is configured to extract oneor more frames from a received transmission stream, a frame includingpayload data encoded into FEC code words each having a predeterminedcode word length and a frame having a predetermined frame length. Asexplained above, a frame comprises a first frame portion having a firstpredetermined length of an integer multiple of the predetermined codeword length and a second frame portion having a second predeterminedlength shorter than the predetermined code word length. The frameextraction section is further configured to extract an FEC code word anda predetermined number of repetitions of said FEC code word from thefirst frame portion of a frame and to extract a selected number of bitsof said FEC code word from the second frame portion of said frame.Further, an FEC decoder is provided that is configured to decode payloaddata from the FEC code words, the repetitions of said FEC code word andthe selected number of bits of said FEC code word extracted from saidframe.

With the disclosed apparatus and methods using repetitions of code bitsin the second frame portion an improvement of the SNR and coding gaincan be achieved. The code bits in the second frame portion are, inaddition to the code words in the first frame portion, used by the FECdecoder by accumulating soft values of the decoded bits in order toincrease the signal level and thus to improve the coding gain and SNR.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present disclosure. As will be understood by thoseskilled in the art, the present disclosure may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentdisclosure is intended to be illustrative, but not limiting of the scopeof the disclosure, as well as other claims. The disclosure, includingany readily discernible variants of the teachings herein, defines, inpart, the scope of the foregoing claim terminology such that noinventive subject matter is dedicated to the public.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single element or other unit may fulfill the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicatethat a combination of these measures cannot be used to advantage.

In so far as embodiments of the disclosure have been described as beingimplemented, at least in part, by software-controlled data processingapparatus, it will be appreciated that a non-transitory machine-readablemedium carrying such software, such as an optical disk, a magnetic disk,semiconductor memory or the like, is also considered to represent anembodiment of the present disclosure. Further, such a software may alsobe distributed in other forms, such as via the Internet or other wiredor wireless telecommunication systems.

The elements of the disclosed devices, apparatus and systems may beimplemented by corresponding hardware and/or software elements, forinstance appropriated circuits. A circuit is a structural assemblage ofelectronic components including conventional circuit elements,integrated circuits including application specific integrated circuits,standard integrated circuits, application specific standard products,and field programmable gate arrays. Further a circuit includes centralprocessing units, graphics processing units, and microprocessors whichare programmed or configured according to software code. A circuit doesnot include pure software, although a circuit includes theabove-described hardware executing software.

It follows a list of further embodiments of the disclosed subjectmatter:

1. A transmission apparatus, in particular for use in a Low ThroughputNetwork, said transmission apparatus comprising:

-   -   an FEC encoder configured to encode payload data into FEC code        words each having a predetermined code word length,    -   a frame forming section configured to form a frame having a        predetermined frame length, wherein a frame comprises a first        frame portion having a first predetermined length of an integer        multiple of the predetermined code word length and a second        frame portion having a second predetermined length shorter than        the predetermined code word length, wherein said frame forming        section is configured to include an FEC code word and a        predetermined number of repetitions of said FEC code word into        the first frame portion of a frame and to include a selected        number of bits of said FEC code word into the second frame        portion of said frame.

2. The transmission apparatus as defined in embodiment 1, wherein saidframe forming section is configured to include only parity bits of theFEC code word into the second frame portion of said frame.

3. The transmission apparatus as defined in embodiment 2, wherein saidframe forming section is configured to include all parity bits or theleast significant portion of the parity bits of the FEC code word intothe second frame portion of said frame.

4. The transmission apparatus as defined in embodiment 2, wherein saidframe forming section is configured to include evenly spread parity bitsof all parity bits of the FEC code word into the second frame portion ofsaid frame.

5. The transmission apparatus as defined in embodiment 1, wherein saidframe forming section is configured to include only information bits ofthe FEC code word into the second frame portion of said frame.

6. The transmission apparatus as defined in embodiment 5, wherein saidframe forming section is configured to include all information bits orthe least significant portion of the information bits of the FEC codeword into the second frame portion of said frame.

7. The transmission apparatus as defined in embodiment 1, wherein saidframe forming section is configured to evenly spread code bits of allcode bits of the FEC code word into the second frame portion of saidframe.

8. The transmission apparatus as defined in embodiment 1, wherein saidframe forming section is configured to include all information bits andpart of the parity bits of the FEC code word into the second frameportion of said frame.

9. The transmission apparatus as defined in any preceding embodiment,wherein said FEC encoder is configured to encode payload data into FECcode words of a systematic code.

10. The transmission apparatus as defined in any preceding embodiment,further comprising a transmission section configured to form atransmission stream from a plurality of frames formed by said frameforming section.

11. The transmission apparatus as defined in embodiment 10, wherein saidtransmission section comprises a modulation section configured tomodulate the data contained in the frames using a chirp modulation or adirect-sequence spread spectrum modulation.

12. The transmission apparatus as defined in embodiment 10, wherein saidtransmission section comprises an encryption section for encrypting thedata contained in the frames, a scrambling section for scrambling thedata contained in the frames and/or an interleaving section forinterleaving the data contained in the frames.

13. A transmission method, in particular for use in a Low ThroughputNetwork, said transmission method comprising:

-   -   encoding payload data into FEC code words each having a        predetermined code word length,    -   forming a frame having a predetermined frame length, wherein a        frame comprises a first frame portion having a first        predetermined length of an integer multiple of the predetermined        code word length and a second frame portion having a second        predetermined length shorter than the predetermined code word        length, by including an FEC code word and a predetermined number        of repetitions of said FEC code word into the first frame        portion of a frame and by including a selected number of bits of        said FEC code word into the second frame portion of said frame.

14. A receiving apparatus, in particular for use in a Low ThroughputNetwork, said receiving apparatus comprising:

-   -   a frame extraction section configured to extract one or more        frames from a received transmission stream, a frame including        payload data encoded into FEC code words each having a        predetermined code word length and a frame having a        predetermined frame length, wherein a frame comprises a first        frame portion having a first predetermined length of an integer        multiple of the predetermined code word length and a second        frame portion having a second predetermined length shorter than        the predetermined code word length, wherein said frame        extraction section is configured to extract an FEC code word and        a predetermined number of repetitions of said FEC code word from        the first frame portion of a frame and to extract a selected        number of bits of said FEC code word from the second frame        portion of said frame, and    -   an FEC decoder configured to decode payload data from the FEC        code words, the repetitions of said FEC code word and the        selected number of bits of said FEC code word extracted from        said frame.

15. The receiving apparatus as defined in embodiment 14,

further comprising a receiving section configured to receive atransmission stream formed from a plurality of frames, a frame includingpayload data encoded into FEC code words each having a predeterminedcode word length.

16. A receiving method, in particular for use in a Low ThroughputNetwork, said receiving method comprising:

extracting one or more frames from a received transmission stream, aframe including payload data encoded into FEC code words each having apredetermined code word length and a frame having a predetermined framelength, wherein a frame comprises a first frame portion having a firstpredetermined length of an integer multiple of the predetermined codeword length and a second frame portion having a second predeterminedlength shorter than the predetermined code word length, by extracting anFEC code word and a predetermined number of repetitions of said FEC codeword from the first frame portion of a frame and by extracting aselected number of bits of said FEC code word from the second frameportion of said frame, and

-   -   decoding payload data from the FEC code words, the repetitions        of said FEC code word and the selected number of bits of said        FEC code word extracted from said frame.

17. A non-transitory computer-readable recording medium that storestherein a computer program product, which, when executed by a processor,causes the method according to 13 or 16 to be performed.

18. A computer program comprising program code means for causing acomputer to perform the steps of said method according to embodiment 13or 16 when said computer program is carried out on a computer.

The invention claimed is:
 1. A transmission apparatus, comprising:processing circuitry configured to: encode payload data into forwarderror correction (FEC) code words each having a first code word length;form a frame including a first frame portion and a second frame portion,the first frame portion having a first length of an integer multiple ofthe first code word length and the second frame portion having a secondlength shorter than the first code word length, by: inserting an FECcode word and a first number of repetitions of the FEC code word intothe first frame portion of the frame; and inserting a number of bits ofsaid FEC code word into the second frame portion of the frame; andtransmit the frame in a Low Throughput Network (LTN), wherein theprocessing circuitry forms the frame to include, into the second frameportion of the frame, either (1) evenly spread parity bits of all paritybits of the FEC code word, or (2) evenly spread code bits of all codebits of the FEC code word.
 2. The transmission apparatus as claimed inclaim 1, wherein the processing circuitry is configured to include onlyparity bits of the FEC code word into the second frame portion of theframe.
 3. The transmission apparatus as claimed in claim 2, wherein theprocessing circuitry is configured to include a least significantportion of the parity bits of the FEC code word into the second frameportion of the frame.
 4. The transmission apparatus as claimed in claim1, wherein the processing circuitry is configured to include informationbits of the FEC code word into the second frame portion of the frame. 5.The transmission apparatus as claimed in claim 4, wherein the processingcircuitry is configured to include all information bits or a leastsignificant portion of the information bits of the FEC code word intothe second frame portion of the frame.
 6. The transmission apparatus asclaimed in claim 1, wherein the processing circuitry is configured toinclude all information bits and part of the parity bits of the FEC codeword into the second frame portion of the frame.
 7. The transmissionapparatus as claimed in claim 1, wherein the processing circuitry isconfigured to encode the payload data into FEC code words of asystematic code.
 8. A transmission method, comprising: encoding payloaddata into forward error correction (FEC) code words each having a firstcode word length; forming a frame including a first frame portion and asecond frame portion, the first frame portion having a first length ofan integer multiple of the first code word length and the second frameportion having a second length shorter than the first code word length,by: inserting an FEC code word and a first number of repetitions of theFEC code word into the first frame portion of the frame; and inserting anumber of bits of said FEC code word into the second frame portion ofthe frame; and transmitting the frame in a Low Throughput Network (LTN),wherein the frame is formed to include, into the second frame portion ofthe frame, either (1) evenly spread parity bits of all parity bits ofthe FEC code word, or (2) evenly spread code bits of all code bits ofthe FEC code word.
 9. A non-transitory computer-readable recordingmedium that stores therein a computer program product, which, whenexecuted by a processor, causes the processor to perform thetransmission method according to claim
 8. 10. The transmission method asclaimed in claim 8, further comprising inserting only parity bits of theFEC code word into the second frame portion of the frame.
 11. Thetransmission method as claimed in claim 10, further comprising includinga least significant portion of the parity bits of the FEC code word intothe second frame portion of the frame.
 12. The transmission method asclaimed in claim 8, further comprising including information bits of theFEC code word into the second frame portion of the frame.
 13. Thetransmission method as claimed in claim 12, further comprising includingall information bits or a least significant portion of the informationbits of the FEC code word into the second frame portion of the frame.14. The transmission method as claimed in claim 8, further comprisingincluding all information bits or a least significant portion of theinformation bits of the FEC code word into the second frame portion ofthe frame.
 15. The transmission method as claimed in claim 8, furthercomprising encoding the payload data into FEC code words of a systematiccode.
 16. A receiving apparatus, comprising: processing circuitryconfigured to: receive a transmission stream via a Low ThroughputNetwork (LTN); extract a frame from the transmission stream, wherein theframe includes payload data encoded into forward error correction (FEC)code words each having a first code word length, the frame having afirst frame portion and a second frame portion, the first frame portionhaving a first length of an integer multiple of the first code wordlength and a second frame portion having a second length shorter thanthe first code word length, and the second frame portion of the frameincludes either (1) evenly spread parity bits of all parity bits of theFEC code word, or (2) evenly spread code bits of all code bits of theFEC code word; extract an FEC code word and a first number ofrepetitions of the FEC code word from the first frame portion of theframe; extract a number of bits of said FEC code word from the secondframe portion of the frame; and decode the payload data from the FECcode words, the repetitions of the FEC code word and the number of bitsof the FEC code word extracted from the frame.
 17. A receiving method,comprising: receiving a transmission stream via a Low Throughput Network(LTN); extracting a frame from the transmission stream, wherein theframe includes payload data encoded into forward error correction (FEC)code words each having a first code word length, the frame having afirst frame portion and a second frame portion, the first frame portionhaving a first length of an integer multiple of the first code wordlength and a second frame portion having a second length shorter thanthe first code word length and the second frame portion of the frameincludes either (1) evenly spread parity bits of all parity bits of theFEC code word, or (2) evenly spread code bits of all code bits of theFEC code word; extracting an FEC code word and a first number ofrepetitions of the FEC code word from the first frame portion of theframe; extracting a number of bits of said FEC code word from the secondframe portion of the frame; and decoding the payload data from the FECcode words, the repetitions of the FEC code word and the number of bitsof the FEC code word extracted from the frame.
 18. A non-transitorycomputer-readable recording medium that stores therein a computerprogram product, which, when executed by a processor, causes theprocessor to perform the receiving method according to claim
 17. 19. Thereceiving method as claimed in claim 17, wherein parity bits of the FECcode word are inserted into only the second frame portion of the frame.20. The receiving method as claimed in claim 17, wherein a leastsignificant portion of the parity bits of the FEC code word is includedin the second frame portion of the frame.